Chalmers University of Technology

University of Technology

Chalmers University of Technology

Supply chains more sustainable by using value stream mapping

Lars Medbo and Carl WänströmChalmers University of Technology

Division of Logistics and Transportation

Chalmers University of Technology

Agenda

• Why value stream mapping?• Background and scope• Two case studies• A method

Chalmers University of Technology

Value stream mapping

• Helps you visualize more than the single process level

• Links the material and information flows• Provides a common language • Provides a blueprint for implementation• More useful than quantitative tools• Links together WCM concepts and

techniques

Chalmers University of Technology

VSM & materials handling – Why?

Conveyor belt

Pick and pack into pallet

Transport with pallet jack

Pack into pallet

Loading with forklift

Quality check

Move with pallet jack to buffer

Put on lid

Strap

Put on label

Transport with forklift to storage

Transport label

Transport with forklift

Transport to preparing area

Recieving registration

Unloading

Inspection counting

Label

Chalmers University of Technology

Production and value stream vs. Materials handling and supply chain

• Large resources on material handling and logistics

• Long lead time• Swedish context (distance, suppliers etc.)• Large possibilities for improvements• Methodology missing

Describe, Evaluate, Compare and Develop Supply Chains

Chalmers University of Technology

VSM – How to determineSupply chain performance?

• Utilisation of recourses- Work load operators- Equipment

• Productivity- Man hour / item*- Machine time / item*

1. Quantity

2. Quality

3. Flexibility• Lead time

• Delivery accuracy• Goods damage• Missing items

* Relation to handled volume of components and packages (different levels)

Chalmers University of Technology

The Performance in the Supply Chain

Chalmers University of Technology

VSM – Materials handling system process mapping variables?

• Type of process and description of process

• Demand (-> takt)• No. of operators• Cycle time (C/T) (process time,

operator man hour time, time in stock etc.)

• Value Creating time / Process time / Man & machine time per item

• Change over time (C/O) / Set-up time (S/T)

• Uptime• Scrap, rework, defective

deliveries

• Shifts• Working hours, breaks, meetings,

indirect tasks, (allowances)• Batch size, delivery volume• Space• Package/item type and size,

Quantity and volume per package • Item characteristics (weight,

volume, fragility etc.) • Transports distance• Frequency of process or transport• Quantity of items• Control of process (information

flow)

Chalmers University of Technology

A case study of value stream mapping in a supply chain

• The product is a metal item that is finished directly from the press operation, i.e. no surface treatment

• The customer approx 250 km from the supplier

• Daily deliveries and even demand

Pre-Conditions

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Supplier Transport 3:e part CustomerTransport

Takt time 67 sec.

VSM – Current StateValue Stream Map

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VSM – Current State

300 units* Buffer in front

of press

PressTransportflat belt

conveyor

Pack into EU pallet with one

collar

Transport with walkie stacker

Transport with reach truck

2 itemscart at

assembly station

Assemble on product at assembly

station

Tow cart train drive to

assembly stn at line 224 units

Cart

Repicking to cart

50 stRepicking-

station

FIF

O FIF

O10days Total 37 processes

Chalmers University of Technology

• What is the real customer requirements?

• Continuous one piece flow

• Pull based planning and control

• Levelled flow

• Linked to the Value Stream Takt

Guidelines for the future state map of the materials handling system cont.

As extended continuous flow as possible:

• As few continuous flows as possible

• As few process steps as possible

• As few storage/buffer places as possible

• As few handling operations as possible

• No overproduction – No “working up” – Smaller batches – One piece

“A smooth flow without detours that generates the shortest lead time, highest quality and lowest cost”M. Rother, J. Shook, Learning to see, 2002

Chalmers University of Technology

Results

• 37 different processes – 3 must exist!• The items were stored at 15 places• Items needed for 2,7 days production were

stored close to the end customer• No delivery had been late and no quality

defects had not been reported in the last 3 months

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Supplier Transport Customer

VSM – Future state

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Item1 Item 1 Item 2 Item 2 Change Change

  Current Future Current Future Item 1 Item 2

Throughput time internal (days) 8,8 4,6 2,8 1,2 -47 % -57 %

Throughput time external transport (days) 1,5 0,7 0,1 0,1 -52 % 0 %

Time in storage (days) 8,7 4,6 2,7 1,2 -47 % -57 %

Items in flow (no. of units) 7 326 4 285 940 406 -42 % -57 %

Transport distance, internal (meter) 786 368 2 076 225 -53 % -89 %

Transport distance, external (meter) 231 000 231 000 112 500 112 500 0 % 0 %

Man hour/item (sec) 10,3 3,6 288 95 -64 % -67 %

Machine time/item (sec) 8,4 0,0 0 0 -100 %  

Number of handling activities 7 4 11 9 -43 % -18 %

Number of transport activities 21 6 10 2 -71 % -80 %

Number of administration activities 9 1 7 3 -88 % -57 %

Number of storage/buffer-places 15 4 13 3 -73 % -77 %

Sum of activities and storage/buffer-places

51 15 41 17 -71 % -59 %

Results